Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
  • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
  • C08J9/125—Water, e.g. hydrated salts
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
  • C08J9/0066—Use of inorganic compounding ingredients
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2333/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Derivatives of such polymers

Definitions

• the invention relates to a method for producing a foam suitable as a material from thermoplastic by mixing the plastic with a blowing agent in the melt and heating the mixture until foaming and cooling below the softening temperature.
• EP-A 493 783 discloses polycarbonate foams which are produced from a mixture of a thermoplastic polycarbonate plastic, a pore-forming additive and a hydrate of an inorganic salt by heating above the softening temperature of the plastic.
• Suitable salt hydrates are e.g. Sulphates of magnesium or zinc containing water of crystallization. When heated, the salt hydrates release crystal water, which acts as a blowing agent in vapor form.
• the salt hydrates are not only particularly cheap propellants, but also have an advantageous effect on the mechanical and fire properties as fillers.
• foams are obtained which gradually corrode, especially in moist air. This phenomenon is probably due to the fact that the dehydrated salts absorb water again with the re-formation of the salt hydrates and with volume increase.
• the invention has for its object to find foaming agents for foaming thermoplastic materials to foam materials, which offer the same advantages as the salt hydrates mentioned, but not how they lead to corrosion of the foam in moist air.
• magnesium and aluminum hydroxide and silica release water in vapor form when heated to 230 ° C. or above and foam up the plastic melt. From the hydroxides or silica used Low-water oxides and hydrated oxides are formed which do not or only insignificantly tend to absorb water again. They have a similarly advantageous effect on the mechanical and fire properties as the salt hydrates mentioned above.
• the invention therefore relates to a process for producing a foam from thermoplastic by mixing the plastic with magnesium and / or aluminum hydroxide or silica as a blowing agent in the melt and heating the mixture until foaming and cooling below the softening temperature.
• Another object of the invention is the foam produced in this way.
• the magnesium and / or aluminum hydroxide or silica is used essentially as the sole blowing agent.
• other components such as water contained in the foamable material or vaporizable organic liquids, exert at most a negligible proportion of the foaming into a foam.
• thermoplastics can be used to produce foams with material quality are processed.
• Thermoplastic materials are suitable which are solid at room temperature and can be processed thermoplastically at temperatures of 200 to 330 ° C without substantial decomposition.
• Polycarbonates, polyether sulfones or polyamides are also suitable.
• the inorganic additives used as blowing agents When heated above 200 ° C., preferably at 230 to 330 ° C., the inorganic additives used as blowing agents give off water in the form of steam, which causes foaming.
• Magnesium and aluminum hydroxide often have only approximately the composition Mg (OH) 2 and Al (OH) 3; one therefore also uses formulas such as MgO- (H2O) x or Al2O3- (H2O) x , where x represents an average value close to 1 or 1.5, which corresponds approximately to the amount of water that can be thermally split off.
• the silica may optionally also be partially in the salt form, provided that no hygroscopic residue remains when heated; For example, thermally dehydratable calcium silicate hydrates are suitable. Mixtures of the blowing agents mentioned can
• nucleating agents can be advantageous for the formation of a fine, uniform pore structure.
• Talc, fine silicon dioxide and titanium dioxide powders in amounts of approximately 0.2 to 15% by weight are suitable, for example.
• Foams are preferably produced in the density range from 100 to 1500 kg / m3, in particular from 200 to 900 kg / m3.
• 2 to 50% by weight of the blowing agent, based on the weight of the plastic portion, is used.
• the Mg, Al or Si content in the finished foam is preferably from 0.5 to 20% by weight.
• the foamable mixture can be produced in various ways. If the thermoplastic melts below the decomposition temperature of the blowing agent, it can be mixed directly into the melt - for example with a kneader or an extruder. If the plastic only melts in the decomposition area of the blowing agent, the components are preferably mixed in the form of dry powders or granules and the mixture is heated under pressure; screw machines are suitable for this. Then let it foam up by relaxation. If this happens in a hollow mold, a single molded body is formed which is removed from the opened mold after cooling. A continuous foam profile can be produced by relaxing in a molding channel. In a corresponding manner, the powdery blowing agent can be mixed into the plastic melt in an extruder.
• a mixture of the powdery starting materials can be heated in a hollow mold, so that a foam body filling the mold cavity is formed.
• a foam body filling the mold cavity is formed.
• the material character of the foam comes in the uniform density and pore structure and the defined spatial shape, e.g. as a board or profile, for expression.
• the porous structure itself is not always of crucial importance for the material properties.
• the application of the invention can, for example, have the purpose of reducing the density of the material, which rises above the content of the unfilled plastic due to the content of inorganic fillers, back into the range of typical plastic densities by means of a weak foaming.
• the material according to the invention is suitable for the typical fields of application of technical foams, e.g. in vehicle and aircraft construction, in particular as a core layer of composite materials that contain metal sheets or plastic layers as cover layers. Such cover layers can be applied directly when foaming.
• foams according to the invention those based on polymethacrylalkylimide polymers with a Mg, Al or Si content of 1 to 10, preferably 2 to 5% by weight are particularly high-quality construction materials are characterized by a high modulus of elasticity, high surface hardness and pressure resistance as well as a high heat resistance (100 to 140 ° C).
• magnesium hydroxide as blowing agent is an increased solvent resistance, for example insolubility in methylene chloride, compared to that of the non-foamed polymethacrylmethylimide.
• Example 1 PMMA foam with aluminum hydroxide
• a profile of 30 x 10 mm was continuously extruded on a foaming system consisting of a single-screw extruder with a screw diameter of 30 mm and a screw length of 32 D, two gravimetric dosing scales, a foam nozzle with subsequent calibration and bead removal.
• a homogeneous mixture of PMMA molding compound (PLEXIGLAS®8H) and 2% talc ("Haichen®II", Brenntag Interplast) was fed in continuously at a rate of 10 kg / h over the one weigh feeder; 1.5 kg / h of Al (OH) 3 ("Apyral®24", vernier Aluminiumwerke) were continuously fed in via the other weigh feeder.
• thermolabile Al (OH) 3 After melting and the thermal decomposition of the thermolabile Al (OH) 3, a profile 30 x 10 mm is formed through the foam nozzle, cooled by a vacuum water tank calibration and removed by means of a caterpillar take-off. The measured melt temperature in the foam nozzle was 250 ° C. A uniformly foamed, mixed-cell profile was obtained. To measure the density, a test specimen measuring 25 x 25 x 10 mm was produced from the foam profile. The density determined according to DIN 53 420 was 724 kg / m3. The mineral filler content was 13.5% by weight, corresponding to 5% by weight of Al.
• Example 2 PMMI foam with magnesium hydroxide
• a mixture of a polymethacryl-methylimide molding compound (PLEXIMID®PLEX 8806, Röhm GmbH) with 5% Mg (OH) 2 and 25% talc was processed with the same test device as in Example 1.
• the measured melt temperature was 290 ° C.
• a uniformly foamed, mixed-cell profile was obtained.
• the density determined according to DIN 53 420 was 492 kg / m3.
• the Mg content was 2% by weight.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Cited By (5)

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• 1993
  • 1993-07-24 DE DE19934324904 patent/DE4324904A1/de not_active Withdrawn
• 1994
  • 1994-07-09 EP EP94110690A patent/EP0635537A3/fr not_active Withdrawn

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